Drivers have been flagged down by police in their search for a teenager after three people were arrested.
Officers have been in Pentir after Frantisek "Frankie" Morris, from Anglesey, went missing two weeks ago.
Frankie was last seen near the Vaynol Arms, in the village in Gwynedd, on Sunday 2 May, a day after going to a rave at a disused quarry.
One of the three suspects is held on suspicion of causing death by dangerous driving, North Wales Police said.
A second man and a woman were arrested on suspicion of perverting the course of justice.
People have told BBC Wales of their "shock" and "sadness" over Frankie's disappearance.
"Local people have taken a great deal of interest as he's been missing for a fortnight and local people have been helping the police", said Menna Baines, councillor for Pentir.
"This is a quiet area where everyone knows everyone else - it's a great shock and we're all concerned about the family."
In Llandegfan, where Mr Morris lives with his family, residents also expressed concerns.
"It's come as an incredible shock", said Councillor Alun Roberts.
"Our thoughts have been with Frankie and his family over the last fortnight.
"We have full faith in the police and we wait now to see what happened to Frankie."
Officers spoke to a cyclist who was caught on CCTV in the area around the time of Frankie's disappearance but he is no longer part of the inquiry.
Ch Insp Owain Llewelyn said: "Due to the ongoing investigation, the road from Pont Felin, Pentir heading towards Waen Wen will be closed until further notice."
He appealed for a number of drivers to get in touch.
Police also want to talk to three male cyclists seen near the pub at about 13:45 BST that day.
Many volunteers have been involved in the search, using drones and dogs.
Ch Insp Llewelyn said "several useful reports and pieces of information" were being assessed.
"If there is anyone who was at the rave at the disused quarry in Waunfawr on Saturday (1 May), please use this link to contact us, anonymously if you prefer," he said.
Frankie was last seen on CCTV pushing his bike past the Vaynol Arms.
More than 30 officers have conducted house-to-house inquiries, and specialists have been reviewing CCTV footage between Pentir and Bangor.
Frankie's brother Robin has said the family, from Llandegfan, Anglesey, was "distraught" over his disappearance.