Northern Territory police hold grave fears for two people who tried to evade a police roadblock by jumping into the Mary River, a waterway known for its high crocodile numbers.
NT Police said they are seeking information from anyone on the whereabouts of 19-year-old Caitlyn Munnich and 25-year-old Raphael Woodhouse.
"Police had set up a random road block," a NT Police spokeswoman said.
"When they tried to stop the car it evaded police.
"Police followed until the car pulled off into bush.
"The pair ran from the car and were seen running towards the river and they jumped in the river."
The Mary River is said to be home to the highest concentration of crocodiles in the Top End.
Three other people were in the car at the time and are assisting police with their enquiries.
'Mary River system is full of salt water crocodiles'
A number of concerned friends and family of the pair have taken to social media to express their concern, several also claimed that Ms Munnich is pregnant.
Duty Superintendent James O'Brien said in a statement that police held "grave fears" for the welfare of the pair.
"The Mary River system is full of salt water crocodiles and we are hoping that these people have made it to safety," Mr O'Brien said.
The pair were last seen near Bird Billabong.
In 2013 Sean Cole, 26, died after being attacked by a crocodile while he and a friend were swimming in the Mary River as part of a 30th birthday party.
