LONDON (AP) — Counter-terrorism police in Britain were investigating an explosion at a hospital Sunday in the city of Liverpool that killed one person and injured another.

Police were called to reports of a blast involving a taxi at Liverpool Women’s Hospital on Sunday morning. Police said they were “keeping an open mind” about what caused the explosion but counter-terrorism police were leading the investigation as a precaution.

“So far we understand, the car involved was a taxi, which pulled up at the hospital shortly before the explosion occurred," Merseyside Police said in a statement. “Work is still going on to establish what has happened and could take some time before we are in a position to confirm anything."

One person died and a man was being treated for non life-threatening injuries.

The Liverpool Women’s Hospital said it immediately restricted visiting access until further notice and patients had been diverted to other hospitals “where possible.”