The Latest on the evacuation of an apartment complex near the University of Minnesota (all times local):

9:30 p.m.

An apartment complex evacuated because of concern about a possible hazardous material is being re-opened and police will guard overnight the one apartment where the report originated.

Minneapolis police spokesman John Elder says residents were allowed back in after it was determined that there is no danger to the public. But he said police have not yet heard back on the testing of a substance, adding: "We don't know what it is."

Earlier, the Minneapolis Fire Department tweeted that the evacuation Tuesday involved an "unconfirmed report of ricin," a poison found naturally in castor beans.

Minneapolis police responded around 4 p.m. to a medical situation possibly caused by a hazardous material in an apartment. Elder says first responders learned the victim had gone to a hospital, and emergency crews began evacuating the building.

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7 p.m.

Authorities are trying to determine if the deadly toxin ricin is the hazardous material that prompted the evacuation of hundreds of people from an apartment complex near the University of Minnesota.

The Minneapolis Fire Department tweeted that the evacuation Tuesday in the Dinkytown area involved an "unconfirmed report of ricin," a poison found naturally in castor beans.

Minneapolis police spokesman John Elder says police and fire crews responded around 4 p.m. to a medical situation possibly caused by a hazardous material in an apartment. Elder says first responders learned the victim had gone to a hospital, and emergency crews began evacuating the building.

A hazmat team entered the building, found the substance and took it to the Minnesota Health Laboratory for identification.

Authorities believe the possible contamination was limited to one apartment.

The Star Tribune reports fire crews evacuated The Marshall, an apartment complex that caters to students, and sealed off the area.