The father of a man who plotted to blow up the New York subways was convicted Friday by a federal grand jury in Brooklyn of destroying bomb-making materials and conspiring to obstruct a federal investigation.

The jury convicted Mohammed Wali Zazi, father of convicted terrorist Najibullah Zazi.

Authorities charged that the son Najibullah was plotting to use explosive devices in the New York subway in September 2009. The son had sent an email messages to a contact in Pakistan seeking key ingredients for constructing a bomb.

The son then rented a car in Denver and drove to New York.  On Sept. 11, 2009, while Najibullah was in New York City, the FBI conducted a covert search of his car and discovered handwritten bomb-making notes, authorities said. Also on that day, a  Queens imam, who had been questioned by authorities about the son,  tipped off the father and son about the investigation.  The son then returned to Colorado.

Subsequently, authorities allege that the father,  Mohammed Wali Zazi, tried to derail the federal investigation into the plot.

Authorities say he denied knowing the imam that tipped him off. He also directed family membes to destroy the son’s chemicals and other bomb-making materials so that the FBI would not find them.

He faces a maximum of 20 years in prison on each of the two counts he was convicted of.