Cameroon midfielder Patrick Ekeng had an enlarged heart but more tests are needed to determine the cause of death, Romanian doctors said Monday after an autopsy.

Ekeng, who played for Dinamo Bucharest in Romania, collapsed on the field during a match on Friday and later died at the hospital.

"I observed a larger heart and for an athlete this hypertrophy means a predisposition to turbulent rhythms and a heart attack," Agerpres national news agency quoted Dr. Abdo Salem as saying.

However, Salem added, he was waiting for lab results.

Dan Dermengiu, the director of the Mina Minovici Forensic Institute where the autopsy was performed, said many athletes have enlarged hearts and that "is not conclusive in the case of his death."

The 26-year-old Ekeng collapsed seven minutes after coming on as a substitute against Viitorul Constanta. He was taken a short distance to a hospital where doctors tried for more than an hour to resuscitate him.

Media reported that a doctor from Cameroon took part in the autopsy at the request of Ekeng's family.

Meanwhile, amid criticism about the emergency medical treatment, Romania's interior ministry suspended the license of a private ambulance company that transported Ekeng to the hospital after he collapsed.

The ministry said in a statement late Sunday it found defibrillators with expired batteries in some ambulances belonging to Puls, and medicine used in resuscitation procedures that had expired.

The ministry suspended Puls' license for one month to remedy the situation and fined it 23,800 lei ($6,050).