NORFOLK, Va. — The Navy is offering a $2,500 reward for information leading to an arrest in a series of bomb threats that have disrupted operations this week in Virginia.

The Virginian-Pilot reports that the Naval Criminal Investigative Service is increasing the offered reward from $500 to $2,500.

On Thursday, a bomb threat was written on a bathroom wall at Norfolk Naval Shipyard in Portsmouth.

On Wednesday, a bomb threat was called in to Naval Station Norfolk, followed by five more threats targeting Joint Expeditionary Base Little Creek in Virginia Beach.

The bomb threats were determined not to be credible.

Operations were also interrupted in Norfolk on Monday, when a sailor reported seeing a trespassing scuba diver. The sighting proved unfounded.