Another Austin explosion — perhaps triggered by a trip wire — injured two parties on bicycles Sunday night, leaving police frantically working to determine if the explosion is linked to a trio of box bombings that have gripped the Texas capital in fear.

The latest smash came around 8: 30 p.m. Sunday night in a suburban place known as Travis Country. Investigates didn’t immediately justify what stimulated it.

Austin police Chief Brian Manley said the explosion may have been explosion by a trip wire, including the blast was “activated by someone either treat, kicking or coming into contact with a trip wire that initiated the device” as they strolled or rode their bikes through the area.

There was no immediate word on what made the explosion or if it was related to the three pack missiles that were explosion earlier this month. ( AP)

“That changes things, in that our security word to this detail has been involving the handling of containers and telling parishes ‘do not handle packages, do not pick up containers, do not disrupt packets, ‘” Manley mentioned at a hastily-arranged news conference. “We now necessity all levels of society to have an extra rank of vigilance and pay attention to any suspicious device, whether it be a packet, a crate, a knapsack, anything that looks out of home. Do not approach it.”

Manley said police were “working under the belief” the explosion was related to the three others, but sleuths still had yet to process the entire scene. He urged people within a half-a-mile radius to stay in their homes until at least daybreak.

“We want to put out the meaning that we’ve been putting out and that is , not only do not touch any packs or anything that looks like a package, do not even extend near it at this time, ” Manley spoke at an earlier news conference. Because “we have not had an opportunity to look at this explosion place to actually determine what has happened.”

A witness speaking to FOX7 described hearing a “loud bang, ” adding that it was “not a auto crash , not gunshots but something terrible.”

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Two guys in their 20 s digested non-life threatening harms in the blast, including one who had tacks in his leg, according to KVUE-TV . South Austin Medical Center officials said the men is now in good condition.

A witness speaking to FOX7 described sounding a “loud bang, ” adding that it was “not a vehicle crash , not gunshots but something terrible.” ( AP)

Authorities also issued an emergency alerting on cellular phone after the blast took place.

Austin Mayor Steve Adler articulated late Sunday he was confident dominions were going to find which will provide for the cord of “horrific” detonations, according to KVUE-TV.

Manley urged people within half a mile to stay in their homes. Dominions said they would keep the bordering arena blocked off at least until daybreak Monday for authorities to check the area, according to FOX7.

Sunday’s explosion was the fourth to rock Austin less than three weeks. Nonetheless, the three previous bombs occurred on the eastside of the city.

The locations of all four recent explosions in Austin, Texas ( Fox News)

The first was a bundle projectile that exploded at a northeast Austin home on March 2, killing 39 -year-old Anthony Stephen House. Two more box bombs then explosion farther south on March 12, killing 17-year-old Draylen Mason, wounding his mother and injuring a 75 -year-old woman.

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Police did all three of those were likely related and implied bundles that had not been mailed or put forward by private carrier but left overnight on doorsteps.

Manley initially advocated they could have been hate crimes since all the victims were pitch-black or Hispanic, but now says that investigators aren’t ruling out any possible motive

Earlier Sunday, Austin patrols said here wage for knowledge to move to an arrest in the fatal blowups has risen by $ 50,000 to a brand-new total of $115,000. Manley told more than 500 men, including federal agents, have deported 236 interrogations in follows up on 435 leads.

Fox News’ Michael Arroyo, Nicole Darrah and the Associated Press contributed to this report .

Ryan Gaydos is an editor for Fox News. Follow him on Twitter @RyanGaydos.