Iran on Tuesday said its was investigating the detainment of Iraqi custom officials, the news agency ISNA reported. Foreign Ministry spokesman Hamid-Reza Assefi declined to give more details until the issue was "thoroughly investigated". An Iraqi source said earlier that Iranian security forces Monday detained ten Iraqi customs officials searching an Iranian cargo ship anchored in Iraqi territorial waters near Basra. The source told Deutsche Presse-Agentur dpa that the Iranian ship returned to a port in Iran with the detained Iraqi officials on board.