SAN PEDRO, Laguna, Philippines—Traffic has snarled for at least six hours Monday due to a buildup of vehicles traveling along the southbound lane of the South Luzon Expressway (SLEx), an employee of the Philippine National Construction Corp. (PNCC) said.

The heavy traffic began at around 9:17 a.m. at the Cabuyao exit due to a convoy of about 300 vehicles attending the Iglesia ni Cristo’s 95th anniversary celebration in Calamba City Monday afternoon, PNCC radio operator Rudy Lidris said in a phone interview.

He said the buildup continued up to Mayapa town and Calamba City toll plaza at about 10 a.m.

“The traffic was heavy. Even those [motorists] calling here were already mad at us,” Lidris said.

As of 3 p.m., heavy traffic was seen along Pitang bridge in Sta. Rosa City going to Batangas exit.

Lidris said the vehicles were moving at a slow pace of about “five to ten kilometers per hour or [intermittently] at full stop.”