On each side of the Winnebago River near the Illinois Avenue bridge, Iowa State Patrol officers could be seen painting green circles on the banks of both sides of the river.
The marks will play an important role in the continued search of human remains found on the north shore of the river on March 11.
Law enforcement agencies working with the Mason City Police Department continued the search Thursday, but also sent a drone up to fly over a portion of the river to set up a search grid and map.
"A drone can map a large area much more quickly and that will help with this search," said Iowa State Patrol Lt. Dana Knutson, the commander on scene of Thursday's search.
Knutson said drones have aided ISP with numerous accident scenes and have not only been able to photograph a scene from the air, but also take measurements that once had to be done manually.
"We'll be able to get a map from the drone flyover," said Knutson, who noted that the State Patrol often helps other agencies with searches using its drone.
According to a MCPD press release, clothing and apparent bone fragments were found by a resident on March 11 along the Winnebago River near North Illinois Avenue. Additional bones were recovered by officers who responded to the scene.
The remains and clothing were sent to the state medical examiner's office in Ankeny for analysis. No identification has been made.
In July, a lower jawbone was discovered by kayakers on a rock bed in the Winnebago River, near the North Illinois Avenue bridge, and was turned over to authorities, according to Mason City Police Chief Jeff Brinkley.
The lower jawbone was sent to the Iowa Crime Lab for examination, and were positively identified as Jane Schreur, 31, of Mason City.
Schreur was reported missing in November 2019 and was last seen by her family in May 2019. Her cause of death is unknown.
The circumstances behind Schreur's disappearance were unknown, but officers were prompted to begin an investigation due to Schreur's health history and the amount of time that had passed since she was last seen.
Foul play is not suspected in Schreur's disapparance, however, the case is still under investigation. Anyone with information is asked to contact the Mason City Police Department at 641-421-3636.
Law enforcement hasn't made a connection to that find and the recent discovery along the Winnebago River.
Assisting in Thursday's investigation were the Iowa Division of Criminal Investigation, the Iowa State Patrol, the Iowa Department of Natural Resources, the State Medical Examiner's Office, the Cerro Gordo County Emergency Management Agency, Community Emergency Response Team and City of Mason City Operations and Maintenance.
Birch Drive will be closed from Illinois Avenue to Highway 122 on Thursday while the teams work in the area.
"We appreciate the community's help in keeping the area free of traffic congestion and obstruction while personnel are working in the area," the release said.
Fishermen made the discovery March 22 in a pond in a rural area.