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Update: 10:33 a.m. March 19
More than 250 special agents are working the site of the city's fourth bombing this month, and more help is on the way according Austin Interim Police Chief Brian Manley.

The stay-in-place continues until further notice in the Travis Country neighborhood, likely 2 p.m., as investigators collect evidence and make sure the area is void of other bombs.

Manley said Austin residents should report any "bag, backpack and box" that seems out of place by calling 911. He said it's important, since a tripwire appears to have been used in Sunday's bomb that was left along the road and detonated by two men, ages 22 and 23, who were walking with their bicycles.

Manley said they both have significant injuries from the explosion and are in stable condition at an area hospital.

The city is being assisted by the FBI and ATF, along with the Texas Department of Public Safety and San Antonio Police Department, among others, Manley said in his latest press conference.

Travis Country residents were asked to share any home surveillance video that could help provide information for investigators. Manley asked them to call 512-974-5210 to discuss any video help.

Original post 4:58 a.m. March 19

Austin Interim Police Chief Brian Manley urged residents of the Travis Country neighborhood to stay in place Monday morning so his department; the Federal Bureau of Investigation; and the Bureau of Alcohol, Tobacco, Firearms and Explosives can investigate Sunday night's explosion that injured two men either walking with or riding bicycles.

It is the fourth explosion in the city since March 2. Overall, two people have been killed and several injured as a result of the explosions.

Sunday's explosion at 8:30 p.m., believed to be related to the other three according to Manley, was different than the other three which all included packages that detonated when moved. Manley said the investigation could show a tripwire was used in Sunday's attack, which left two men in their 20s with non life-threatening injuries. The device was along the road, Manley said.

The address given during Sunday's response by Austin-Travis County EMS was at the 4800 block of Dawn Song Drive. Several roads were blocked off as dozens of investigators went to the scene. The Travis Country neighborhood is west of Mopac and north of Southwest Parkway. It is bordered to the north by Barton Creek Wilderness Park and the Barton Creek Greenbelt.

During a press conference overnight, Manley said the investigation needs to continue with daylight and residents should call 911 to report any suspicious packages, backpacks or other items they see that look out of place.

Austin ISD officials said they are working with APD to assure the safety of their students and will not send buses to the Travis Country neighborhood on Monday morning. Manley and Austin ISD confirmed tardies or absences of children living in that neighborhood will not be counted against them on Monday.

Manley said residents of the Travis Country neighborhood, if they need to move from their house because of an emergency, should call 911 and wait for officials.

Sunday's blast came just hours after Manley announced the reward for information leading to an arrest and conviction in the bombing cases has been raised to $115,000.