ANKARA, Turkey (AP) — The U.S. Embassy in Turkey says it is preparing to resume regular services after a security threat forced it to close for a day.

The embassy in Ankara was closed on Monday as police in the Turkish Black Sea coastal city of Samsun detained four Islamic State suspects while investigating a possible attack plot involving the American facility.

Only limited services were provided on Tuesday, but spokesman David Gainer says the embassy "will be operating as normal" on Wednesday.

Police had stepped up security, searching pedestrians before allowing them to enter the street where the U.S. Embassy and other buildings are located.

In 2013, a suicide bomber detonated an explosive in front of the embassy, killing himself and a Turkish guard.