A team of Lithuanian investigators recovered the black boxes from Monday's deadly cargo plane crash, as they began their probe into what caused the aircraft to go down and worked to clear the crash site.
Investigators from the U.S. were dispatched to aid in the investigation, officials said. German aviation experts had arrived to help, while Spanish investigators were expected to arrive later Tuesday.
The jet crashed on Monday morning less than a mile from the runway at Vilnius International Airport, officials said. One of the four people onboard was killed in the crash, local officials said.
Lithuanian police and prosecutors have opened a "pre-trial" investigation into the crash, according to Prime Minister Ingrida Šimonytė, whose office held a meeting late Monday on the government response.
MORE: DHL cargo plane crashes in Lithuania, killing 1, local officials sayThe government has ordered an investigation under the country's criminal code, which calls for probes into "'Improper maintenance or repair of vehicles or roads, or of equipment thereon,' which provides for liability in the event of loss of life, serious injury to persons or very serious damage to property," the prime minister's office said.
"I urge everyone to have confidence in the investigating authorities' ability to conduct a thorough and professional investigation within an optimal timeframe," Šimonytė said in a statement. "Only these investigations will uncover the true causes of the incident—speculation and guesswork will not help establish the truth."
The investigation will be led by the Ministry of Justice of the Republic of Lithuania Transport Accident and Incident Investigation Division, with aid from the U.S. National Transportation Safety Board, the board said on Monday.
The results of that investigation are expected to be made public, the NTSB said.
Lithuanian officials said on Tuesday that they expected the inspection of the crashed plane to be mostly completed within three days, at which point the destroyed plane will be removed from the site. Officials told reporters that they were searching for a hanger where they can begin to place aircraft parts.
The DHL cargo plane -- a Boeing 737-476 operated by Swiftair -- had flown into Lithuania from Germany. It crashed in a residential area in Liepkalnis, on the outskirts of the capital, Vilnius, the Lithuanian airport authority said in a statement posted on social media on Monday.
One of the pilots, who was from Spain, was pronounced dead at the scene and the other was transferred to a local hospital in critical condition, Bozena Jerenkovic, a medical doctor who was part of the emergency team on site, told ABC News on Monday. It appeared that the cockpit had been separated from the plane's fuselage, she added.
The Lithuanian National Crisis Management Center confirmed to ABC News that the pilot is in critical condition. The other two people who were injured in the crash are doing OK, the center said.
ABC News has reached out to Bonn, Germany-based DHL for comment.
ABC News' Joe Simonetti and Melissa Gaffney contributed to this report.