A bomb explosion occurred in Austin, Texas Sunday night, injuring two young men. FBI and local law enforcement swarmed the area, in an effort to determine if it is related to the previous three package bombings that have occurred in the city within the past month.

Hours after the Federal Bureau of Investigation in San Antonio announced they were increasing the reward to $100,000 for information leading to the arrest and conviction of the person or persons responsible for the package bombs which have injured and killed several Austin residents, a fourth bomb went off about 8:30 pm Sunday night.

In Sunday night’s bombing, two males in their 20’s were injured, but their injuries are not considered life-threatening, the Austin Police reported.

Austin police Chief Brian Manley said one of the men injured in Sunday night’s attack had nails in his leg, and police were examining a suspicious backpack.

ABC News reported late Sunday night: A law enforcement source tells ABC News it will take some time to determine whether the explosion at about 8:30 p.m. local time Sunday night is linked to the earlier bombings. The bombings this month, over an 11-day period, killed two people and injured two others.

The Austin Police Department responded to a so-called “Bomb Hotshot,” according to a tweet. It urged anyone in the “4800 block of Dawn Song Dr.” to avoid the area. It said the victims had “unknown injuries.”

Austin Police Chief Brian Manley issued a “safety alert” in the wake of the bombing, urging people located within a half-mile radius of where the incident occurred to stay indoors.

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