DETROIT -- The Wayne County Medical Examiner’s Office said Monday it would not yet release autopsy results for three men who collapsed and died while running in the Detroit Free Press/Flagstar Marathon Sunday.

A spokesperson for the office said there's no timetable on when the results would be released, but that toxicology results could take up to six weeks.

Family and friends of three half-marathoners said the runners had trained for the race and they were unsure what could have caused the deaths.

Daniel Langdon, 36, of Laingsburg, collapsed at about 9:02 a.m. Sunday between the 11- and 12-mile markers, said Rich Harshbarger, vice president of consumer marketing for the Detroit Media Partnership.

Rick Brown, 65, of Marietta, Ohio, collapsed at 9:17 a.m., near where Langdon went down, and 26-year-old Jon Fenlon of Waterford collapsed at about 9:18 a.m., at the finish line after running the 13.1-mile half-marathon in 1:53:37, Harshbarger said.

Harshbarger said there were 60 medical professionals along the route, including 14 doctors, and that the men received medial assistance within seconds of their collapse.

All three were taken to Detroit Receiving Hospital, where they were pronounced dead.

"It's very upsetting to see any runner to train so hard and then collapse right at the finish line," Harshbarger said.

Every runner must sign a medical release form, and they are encouraged to talk to their doctors before they run the race, Harshbarger said.

Harshbarger said he saw Fenlon cross the finish line.

"He just appeared to be slightly in distress, wobbly legs. He was getting close to the finish line and that's when medical professionals saw that he was beginning to collapse ... that's when they took over and did their work," Harshbarger said.

DMC Dr. Devon Moore was one of the first responders who treated Fenlon.

“He was on the ground, unresponsive, not breathing,” Moore said.

The medical director for the event, DMC Dr. Jenny Atas, said there were three medical stations along the route that had defibrillators.

When asked how long it took for medical personnel to get to the men who collapsed, Atas said, “One of them dropped right at the foot of one of our physicians who had the AED in her hand. So you couldn’t have been quicker, it was within 30 seconds or even 10 seconds of them dropping on the course that they had electricity applied.”

Atas said the other two men received treatment between two and three minutes.

“The course was set up very well. You have spotters along the course and then your medical teams strategically located in between the spotters,” Atas said.

Atas said she believes the outcomes would not have been different had there been any more medical personnel or medical equipment on site.

Atas also said there was a total of 220 medical incidents that were treated Sunday.

Laura Fenlon said her son had always been an athlete and she did not know of any medical problems he may have had. He played soccer and worked out, and was doing his first half-marathon.

Jon Fenlon's name has appeared in previous news headlines in October of 2006. He caught a home run ball hit by the Detroit Tigers' Magglio Ordonez in a game against the Oakland A's. The move sent the Tigers to the World Series. Fenlon graduated from Eastern Michigan University in 2007. He worked at a junior art director at Campbell-Ewald Advertising.

"To see something like that happen to someone so young ... it makes you stop and think, " said Fenlon's neighbor, Susan Briggs.

Brown was an avid runner. He was at the marathon with his wife and many friends from his running club, the River City Runners & Walkers Club.

The club released a statement Monday about Brown’s death. It read in part, “Rick was an icon in this area as a runner and as someone who was always willing to help others with their training and running … he will be missed by everyone in our club and in our area.”

Brown started running about 30 years ago, said Joe Corra, a longtime friend. He had asbestosis, a lung disease, but had been cleared to train and had previously participated in regional marathons.

Langdon was celebrating his 36th birthday running the race Sunday.

Richard Poling, Langdon's stepfather-in-law, said Langdon, a father of three, was an avid outdoorsman and hunter.

"As far as we knew, he was in excellent health," Poling said.

Harshbarger said it is suspected that the men died from cardiac arrest, but that an autopsy would determine the exact cause of death.

The only other death in the event's history occurred in 1994, when a 42-year-old Troy resident collapsed and died during the race.

"On a day when so many people bring such energy and challenge themselves to do their utmost, this news is very difficult to hear," Free Press editor and publisher Paul Anger said. "Our deepest sympathies are with the families."

Deaths at marathons are relatively rare.

According to a Toronto study, which was published in a Runners World December 2008 article, there were 26 heart-attack deaths among 3,292,000 American runners who competed in 750 marathons over the past 30 years. That's a risk of 1 death per 126,000 runners.

More than 19,000 people were registered to participate in the 32nd Detroit Free Press/Flagstar Marathon on Sunday. The event kicked off just after 7 a.m., and included the marathon, half-marathon and a 5K.

Slideshow: Free Press/Flagstar Marathon 2009

Nicholas Stanko, of Haslett, Mich., took first place in the marathon with a time of 2:20:23.

Sara Plaxton, of Highland, Mich., was the top female placer in the marathon with a time of 2:57:09.

For the half-marathon, Detroit resident Ryan Piippo finished first with 1:13:11 and Angela Matthews, of Westland, Mich., made out with a top time of 1:18:52.

The winner of the disabled race was Travis Peruski, of Linden, Mich., with a time of 1:38:57.

For a complete list of race results, click here.

To see the course runners took, visit www.freepmarathon.com.