DENISON, Iowa -- Investigators in Des Moines have removed the bodies of 11 people from a grain storage rail car, but it may be several months before all the details are known.

The bodies were first discovered at the Archer Daniels Midland plant two miles west of Denison on Highway 30.

The bodies were found around 3:30 p.m. Monday afternoon when crews at the plant were filling the train cars. An official with the Immigration and Naturalization Service said it appeared all of the victims were from Mexico, however their exact nationality has not yet been determined.

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INS District Director Jerry Heinauer said the Mexican consul told him the rail car left Matamoras, Mexico, in June. It had been parked in Oklahoma for several weeks before being pulled to Denison to be loaded.

Investigators said the rail car could have been opened from the inside, but the car was locked with an outside latch, trapping the people inside.

Heinauer said authorities don't yet know if the victims were being smuggled into the country. However, he said the case fits the pattern of some smuggling operations. Investigators said the bodies were badly decomposed.

The car was hauled to Des Moines Monday night where the Department of Criminal Investigations will be able to better investigate the case.

On Tuesday morning, investigators made preparations to remove the remains. Investigators cut a larger opening in the car to remove the bodies without disturbing them.

Officers removed 11 bodies from the car. The remains will now be examined by medical examiners and forensic anthropologists. Investigators said the process of examining each body could take several months.