The explosion, which killed three and injured seven people, occurred in the town of Pavshino at 9:10 a.m. Moscow time (6:10 a.m. GMT). It completely ruined the brick plant building and damaged residential houses in the radius of six kilometers (3.7 miles) from the scene.
"One of the factories in the area of Krasnogorsk could have drained explosive substances [into the sewage systems] - acetone, gasoline or some other inflammable liquids," said Alexei Panteleyev, deputy governor of the Moscow Region.
Emergencies officials said earlier a high gas content inside the plant could have triggered the explosion without elaborating on a source of the gas leak.
Panteleyev said 19 enterprises working in the region were being checked for the possibility.
He said 260,000 people had been left without water supplies. Drinking water has been supplied in trucks.
Authorities said that water supplies would be restored Monday and measures had been taken to prevent sewage spills into the Moskva River located 150 meters (492 feet) from the scene.
Three victims to the explosion are in hospital with serious burns and brain injuries, but doctors said their lives were out of danger. The others have been released from hospital after receiving medical aid.
The explosion damaged 19 residential houses in the region, shattering windows and doors. Roofs and walls were seriously damaged in five buildings. Authorities started repairs after inspecting the buildings.
