Pro-Russian separatists in eastern Ukraine fired a warning shot Friday and blocked Organization for Security and Cooperation staff from investigating the crash site of Malaysia Airlines Flight MH17, according to reporters tweeting from Ukraine.

"Shots fired by rebels at international team of investigators (OSCE) in Ukraine as they approach plane wreckage," Terry Moran, chief foreign correspondent at ABC News, tweeted Friday afternoon.

BREAKING: Shots fired by rebels at international team of investigators (OSCE) in Ukraine as they approach plane wreckage, via @KiritRadia — Terry Moran (@TerryMoran) July 18, 2014

About 30 OSCE investigators arrived at the crash site on Friday by helicopter, after the United Nations Security Council demanded a thorough and independent international investigation into the crash that killed 298 passengers. Ukrainian military and pro-Russian rebels accuse each other of shooting down the plane.

BREAKING NEWS: Shots fired by rebels at international team of investigators (OSCE) in Ukraine as they approach plane wreckage. — Jerry Liet (@jerryliet) July 18, 2014

According to Guardian reporter Harriet Salem, rebels turned away the OSCE investigators on Friday. But Reuters reported that pro-Russian separatists said they welcomed the investigators and denied reports to the contrary.

Ukrainian photographer Pierre Crom said on Twitter the rebels fired a warning shot into the air.