Massachusetts Water Resources Authority officials say they've identified couplings on eight other projects similar to the one that failed on Saturday, leading to a boil water order for much of eastern Massachusetts.
Officials said Thursday they will inspect each of the couplings, some of which are underground, to make sure they are stable.
Although the couplings are of the same design, none are of the same size of the coupling that held together the two sections of the 10-foot pipe that gave way last weekend.
Officials said they are searching records to see if there are even more of the couplings on other projects.
Investigators continued scouring the Charles River using metal detectors and ground penetrating radar Thursday to find the missing coupling.
The MWRA board voted Thursday to form a special commission to study the incident.
This program aired on May 6, 2010. The audio for this program is not available.