Counter-terrorism police in Britain are 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 that pulled up at Liverpool Women’s Hospital shortly before the explosion took place Sunday morning.

Police said the explosion had not been declared a terrorist incident, but counter-terrorism police were leading the investigation as a precaution.

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

Police said they were “keeping an open mind” about what caused the explosion.