The Mexican government says it is launching a formal search for 19 migrants who were pulled from a bus by armed men in the northern border state of Tamaulipas.

The National Commission for Missing Persons said Wednesday the search includes the Tamaulipas state police, the army, federal police and prosecutors.

The country's top security official said Tuesday that in addition to the 19 seized last week, 25 others were kidnapped last month from a different bus, for a total of 44.

The search effort announced Wednesday refers specifically to the more recent incident.

The government hasn't specified the nationalities of the victims, but they are believed to be from Central America.