Police in west California tighten security on rail transport following New York subway blast

SAN FRANCISCO, Dec. 11 (Xinhua) -- The police authorities of the Bay Area Rapid Transit System (BART) in San Francisco, a major tourist city in the U.S. west coast state of California, have tightened security on the popular intra-city rail transportation service following an "attempted terror attack" in New York on Monday.

An explosion hit a New York subway station close to Time Square early Monday morning, in which four people were injured in a passageway near Times Square, Manhattan in New York City.

Police have identified the 27-year-old suspect as Akayed Ullah and have kept him in custody. New York City Mayor Bill de Blasio said the incident was an attempted terrorist attack.

"BART Police will maintain high visibility and awareness today in response to #NYC incident. We ask our riders to always report suspicious activity," the BART authorities announced on its twitter.

BART is a main rail transportation system for the San Francisco Bay Area, a populous region surrounding the San Francisco, San Pablo and Suisun estuaries in California. About 7.68 million people live in the nine-county Bay Area which contains many cities, towns, airports, as well as regional, state, and national parks.

An average 430,000 trips were recorded on weekdays for the BART system, and about 129 million people choose it as their daily commute service every year. Enditem