NEW YORK (Reuters) - Nisource on Wednesday was investigating the cause of a natural gas pipeline explosion on its Columbia Gas Transmission line that rocked a small community near Charleston, West Virginia, a day earlier, the company said.

The cause of the blast, which occurred around 1 p.m. EST and set several nearby buildings on fire, remained unknown, Nisource said.

"Columbia Transmission teams are working today to help identify exactly what caused the incident," Nisource said.

The 20-inch pipeline is part of the company's network that delivers gas to local utilities. Service to those customers was not affected, said Nisource, which provides natural gas, electrical power and related services to 4 million U.S. customers.

"Gas has been rerouted in the area to allow for no impact to commercial operations," Nisource said.

(Reporting By Edward McAllister and Eileen Houlihan; Editing by David Gregorio)