Ridgefield (AP) -- A lockdown has ended at schools in Ridgefield after police found no sign of any dangerous activity.

The school system posted a message on its website on Monday saying that police had authorized schools to reopen. However, a police presence remains at each school.

Police said earlier in the day that schools were locked down after an unspecified "suspicious incident."

School officials are on heightened alert three days after a gunman fatally shot 20 children and six adults at an elementary school in Newtown, about 18 miles from Ridgefield

Ridgefield's school superintendent Deborah Low released a statement at 9 a.m. warning of a possibly suspicious person in the Branchville train station area. She said Branchville Elementary school buses had been diverted to another school.