MEXICO CITY (Reuters) - Mexico has arrested a former police chief at the heart of an investigation into the disappearance and likely massacre of 43 trainee teachers in the southwestern city of Iguala two years ago, security officials said on Friday.

Felipe Flores was chief of police in Iguala when the students disappeared on the night of Sept. 26, 2014. He was one of the people most likely to know what happened to the students, according to experts on the case, which hugely embarrassed the government.

Flores, who had been a fugitive for two years, was arrested while visiting his wife in Iguala, national security commissioner Renato Sales told a news conference.

According to the government's initial findings, the 43 were abducted by corrupt police in Iguala and handed over to a drug cartel, which mistook them for members of a rival gang. Then, the government said, they were murdered, incinerated and ground up, and their remains dumped in a nearby river.

So far, the remains of only one of the 43 students have been definitively identified. The parents of the missing are still pressuring the government hard for answers.

A group of international experts who reviewed the evidence sharply criticized the government's version of events, helping to dent the credibility of President Enrique Pena Nieto.

(Reporting by Lizbeth Diaz; editing by Grant McCool)