Four Islamic State terror group suspects were detained on Monday after the U.S. Embassy in Turkey was shut down due to a security threat, reports said.

The four Iraqi nationals were arrested during an investigation into a possible attack on the U.S. Embassy in Ankara, Turkish state media reported. Two of the suspects were detained on a bus while traveling on a highway linking the Black Sea city of Samsun to Ankara. They were taken into custody at a security check.

Two others were detained in Samsun.

The arrests came after the U.S. Embassy had shared intelligence with Turkey’s intelligence and security authorities, Turkish Deputy Prime Minister Bekir Bozdag said. The intelligence, on the possible attacks against the embassy or Americans, led to "important results." He said the U.S. diplomatic missions in Istanbul and the southern city of Adana remained open for business.

The embassy announced on its website the building will be closed Monday and Tuesday due to a “security threat,” but did not provide further information.

“The Embassy will announce its reopening, once it resumes services,” the statement read.

Police searched pedestrians passing through the street in front of the embassy’s main gate.

In 2013, a suicide bomber detonated an explosive in front of the U.S. Embassy in Ankara, the Turkish capital. He killed himself and a Turkish guard. Turkish officials blamed the attack on domestic leftists.

The Associated Press contributed to this report.