For the second time within two weeks, a crash involving a 15-passenger van used for a church trip has led to multiple deaths. Research has shown that these vehicles become less stable and more dangerous when loaded with 10 or more people.

In the latest incident, a Georgia pastor and three others were killed on Sunday when the van carrying them to a church revival blew a tire and flipped several times on a highway, ejecting all on board.

The church van, a 1987 Dodge Ram Wagon, appears to have been overloaded with 19 passengers on board when it crashed, four more than its stated capacity.

Fifteen passengers who survived the crash were taken to hospitals, the AP reports. Their conditions were not immediately known. The passengers were from the Tabernacle of Prayer and Deliverance in Columbus, Ga.

In the previous accident, which also happened after a tire blew out, a Ford van in New York with 14 passengers crashed, killing six people. The crashes have renewed safety concerns about 15-passenger vans, which Fair Warning reported, have provoked warnings in the past from the National Highway Traffic Safety Administration.

In 2001, the agency issued its alert that such vans, especially older models, are markedly less stable when loaded with 10 people or more. The reason is that passengers ride above the center of gravity, making a van increasingly top-heavy, and therefore less stable, with each additional rider.

A spokesman for the Georgia State Patrol said it appeared that none of the passengers in Sunday’s crash was wearning a seat belt. Similarly, many of the passengers in last month’s New York crash apparently were not wearing seat belts, causing them to be ejected.