Updated

Two of the four men arrested on terrorism charges were recent converts to Islam, and that could have played a role in what authorities in California say was an alarming radicalization.

Experts said Wednesday that recent converts can be more susceptible to manipulation and outside influences because they don't have a full understanding of the faith and can seek religious guidance from the wrong people.

Three of the men, all in their early 20s, were arrested Friday as they were about to leave for Afghanistan and meet with the fourth suspect.

The men are charged with plotting to kill Americans and destroy U.S. targets overseas by joining al-Qaida and the Taliban.

The man in Afghanistan was also arrested by authorities there.

Their attorneys have not returned calls.