Following a months-long investigation, Dutch police have arrested seven men they believe were plotting to carry out a major terrorist attack against "a large event in the Netherlands," according to NPR.

The criminal investigation began in April 2018 with information from the General Intelligence and Security Service.

The plan was presumed to involve an attack with bombs and Kalashnikov AK-47s at an event and detonating a car bomb at another location, according to a statement released by Dutch authorities.

During their arrest, the men were in possession of five small arms, authorities said.

The suspects were to be brought before the judge-commissioner in Rotterdam on Friday.