A lockdown at Lakeland High School on Tuesday was cleared after police searched the school for a threatened bomb.

The school was in Code Yellow for about an hour after a written bomb threat was found on a bathroom wall shortly before lunch. State police responded and searched the school.

According to a letter from Principal Thomas Whitley sent home with students, the threat was the second discovered in the past two days.

On Monday, a staff member found a written bomb threat inside a different bathroom stall. The fire marshal conducted a sweep of the school and it was declared safe to hold classes Tuesday, according to the text of the letter sent by spokeswoman Bethanne Bradshaw.

Tuesday morning, the school was placed on lockdown for a regularly scheduled visit by the Suffolk Police Department and its drug dogs. Later in the day, a second written note was found.

“After a thorough investigation, no evidence of a threat was found,” Whitley wrote. Extra precautions will be taken in coming days, including metal detector searches of those entering the building.