The number of persons arrested in connection with the January 18 Harni boat tragedy, which killed 12 students and two teachers, in Vadodara in Gujarat reached 13 on Monday after four persons were held, a police official said.

The four comprise three partners of Kotia Projects, the private firm which was given a contract by the Vadodara Municipal Corporation to manage a recreation zone at Motnath lake, and a sub contractor, the official informed.