LAKE CITY, Minn. (AP) - It may be several days before investigators determine the cause of an anhydrous ammonia leak that forced the evacuation of part of Lake City.

The Iowa, Chicago & Eastern Railroad will be working with the Canadian Pacific Railway to determine why a problem developed with a valve on a customer's tanker car that carried 28,000 gallons of anhydrous ammonia, said Jafar Karim, a spokesman for the IC&E in Sioux Falls, S.D.

Local officials said only a small amount of the ammonia leaked out Saturday morning in Lake City. The noxious fumes forced the evacuation of about 100 homes in the Edge O' Town mobile home park on U.S. Highway 61 on the south side of Lake City.

But authorities said no one was reported injured or required medical treatment directly related to the ammonia leak.

The leaking car was part of an IC&E train that was running on Canadian Pacific tracks and had been picked up in the CP yard in St. Paul earlier Saturday, Karim said.

Jennifer Meyer was preparing her children, ages 8 and 3, for an outing with their father when a police officer knocked on her door at 8:30 a.m. and told Meyer she had to get her family out, right away.

Meyer, who once trained as an emergency medical technician, said she knew it was a warning to take very seriously.

"I knew that anhydrous ammonia is not something to mess around with," she said.

She hustled her children out, taking them and her mother to the Red Cross evacuation site at a Lake City church, where they spent the day playing games, eating donated meals and waiting for word when they could return home.