The 42 foot long tugboat Andrew J. capsized and sank while locking through the west lane of the  Welland Canal.   The Andrew J. along with the tug Kimberly Anne had entered the lock with a barge.   As the locked filled with water, the Andrew J. lost stability, capsized and sank in the lock.  The captain of the tug, the single occupant of the tug, was able to escape.   No reports of injuries.   Some diesel fuel was released into the water.   A large crane was brought in to assist with salvaging the tug.   Authorities have launched an investigation into the incident.