EPHRATA — Bomb threats emptied Ephrata High School two days in a row and police on Tuesday arrested a 15-year-old male juvenile, anticipating charges of threats to bomb or injure property and two counts of intimidating a witness, police said.

On Monday, students and staff were evacuated from Ephrata High School after a bomb threat was received around 7:46 a.m., the Ephrata Police Department reported.

Classes resumed around 11 a.m. on Monday, following a search of the school. No suspicious devices were found and there were no injuries, said Ephrata Police Chief Joe Varick.

Monday's bomb threat was phoned into the school by an unidentified juvenile male caller, Varick said.

The Grant County Sheriff's Office assisted in the search and initial investigation. The Grand Coulee Police Department provided an explosives detection dog. The Ephrata Fire Department and city public works department also assisted.

Police are still investigating that threat.

On Tuesday, a male caller phoned the Multi Agency Communications Center, saying there was a bomb in "all Grant County Schools."

Students and staff were again evacuated from Ephrata High School, but a sweep of the school failed to turn up the suspected device.

All school districts in Grant County were notified of the threat Tuesday. Royal City and Warden high schools were evacuated; Moses Lake, Mattawa, Quincy and Soap Lake high schools were not.

The dispatch center turned over the cell phone number used and investigators determined the phone was stolen the previous day.

Witness information lead to the arrest of the 15-year-old juvenile who was booked into Grant County Juvenile.

The second threat is also under investigation.