US police launched an investigation into the alleged arson at California mosque after a note related to a terrorist attack in New Zealand was discovered near the building, CNN reported.

The incident occurred on Sunday morning in the mosque of the city of Escondido.

According to the police, there were seven people in the building at the time of the fire.

Several people in the mosque came outside and extinguished the fire before authorities arrived, the source noted.

Yusef Miller, a member of Escondido's Islamic community, encouraged fellow Muslims "to make sure you're hypervigilant.”

"It was especially alarming to have it happen this morning, and everybody is on edge here today," Miller said. "Given what's been going on around the nation, around the world, we're not too surprised. We try to stay vigilant, but this can happen to anyone anywhere."

As reported earlier, 50 people have been killed, some 50 injured as the result of two attacks in Christchurch, New Zealand on March 15.

The attack was committed by 28-year-old Australian Brenton Tarrant. Before the attack Brenton Tarrant distributed on the web and sent some politicians his manifesto containing anti-migrant and anti-Muslim wordings.

Tarrant was shooting the attack on video which was dismantled on social media. Facebook said they deleted 1.5 million videos of the attack over 24 hours. After the attack New Zealand's government decided to ban automated guns and rifles.