MANILA, Philippines - Around one in five buses plying routes in Metro Manila are still unaccounted for and may be running their routes without the proper franchises, according to the Land Transportation Franchising and Regulatory Board (LTFRB) said.

In a statement, the regulator said 10 passenger bus companies operating a total of 2,732 buses have been asked to explain why they refused to comply with a recent government audit, aimed at creating an inventory of buses in Metro Manila.

These companies account for about 20 percent of passenger buses operating within Metro Manila, including those with connecting routes to the provinces, which still have to be covered by the audit meant to ferret out the so-called ?colorums? or public utility vehicles operating illegally.

Transportation Secretary Jose de Jesus said the inventory of buses, first done in October 2010, was ?necessary to identify passenger buses operating illegally.?

Companies that have refused to subject themselves to the government audit are A&B Liner, Fermina Express, Admiral Transport, Hi Star, Mayamy Transport, California Bus Line, Genesis Transport and Bus Operator Transport Service Coop. Individual operators, meanwhile, were Roberto A. Barreto and Josephine Lopez.

The government has blamed illegal buses for heavy congestion on Metro Manila?s major thoroughfares. Illegal buses also increase competition for passengers, eroding revenues for legitimate bus operators.

The LTFRB audit will involve the inspection by government personnel of operators? fleets to determine if these firms have buses that are not properly registered.

LTFRB chairman Nelson Laluces said based on the agency?s records, a total of 12,689 passenger buses operate within the metropolis. Of this number, 3,732 units ply the Epifanio de los Santos Avenue (Edsa) route; 1,589 are Metro Manila buses with non-Edsa route.

About 4,300 are provincial liners allowed to use Edsa to reach their respective terminals and 3,088 are also provincial buses which do not to run through Edsa.

He said around 80 percent or 9,957 units of the total number of buses have been submitted to the LTFRB inventory. ?The LTFRB has summoned the 10 operators of the 2,732 bus units, which were not submitted to the inventory,? Laluces said.

He added that failure to justify their failure to comply with the inventory during the subsequent hearings could mean cancellation of the franchise.

Transportation Undersecretary for Road Transport Dante Velasco likewise said he had ordered LTFRB and Land Transportation Office personnel to step up efforts to apprehend illegal buses.

?Operatives of the DOTC Action Center, LTFRB, LTO can easily apprehend unregistered public utility buses that contribute to traffic congestion and pose undue competition to legitimate public utility operators,? Velasco said.