Lawrence police have not yet identified a suspect in three Lawrence bomb threats called in early Sunday morning, said Lawrence Police Sgt. Trent McKinley.

Two of the 911 calls came about 2 a.m. Sunday and threatened violence with bombs and firearms at both Lawrence Walmart stores, at 550 Congressional Drive and 3300 Iowa, McKinley said.

On Monday morning, McKinley reported that similar threats also had been called into Lawrence Memorial Hospital switchboard Sunday, just minutes after the Walmart calls. Hospital staff contacted police.

In all of the cases, police responded and assisted in searching the buildings threatened, but nothing dangerous was discovered, McKinley said.

Similar false threats were made just before 4:30 a.m. Sunday toward a Walmart in Leavenworth.

These threats come on the heels of a string of false threats made last week in Missouri and Oklahoma.

The Associated Press reported that stores in eight Missouri communities had received similar threats on Friday. A false bomb threat shut down a store in Claremore, Okla., on Wednesday.

An FBI spokesman said it is investigating the series of threats made across the area, and it would be working with local law enforcement as part of an ongoing investigation.