Bulgarian police have detained 47 illegal immigrants in the village of Herakovo, some 20 km northwest of the capital, the Ministry of Interior said in a statement on Tuesday.

The police operation was held on Monday after receiving information that "persons looking like immigrants" were in the yard of a house in the village, the statement said.

The foreigners, including 24 men and 23 underage boys, did not have any identity documents, it said.

Four identified themselves as Pakistanis and the rest -- as citizens of Afghanistan, it added.

The investigation is ongoing.

Bulgaria is located on a migrant route to Central and Western Europe. According to official data, the Ministry of Interior arrested 2,989 illegal immigrants in 2017.