Two grade three pupils from Nyatwoni Primary School in South Mugirango, Kisii county, drowned in Nyasanta River on Thursday afternoon.
The bodies were retrieved and taken to Kisii Teaching and Referral Mortuary to await postmortem.
The teacher who had accompanied them was arrested.
"We have already picked him as we commence a probe," said Kisii County Police Commander Jebel Munene.
There are conflicting reports on whether the learners were out learning nature or swimming.
A teacher however, said the pupils had been taken to study about tides at the river only for the two boys to meander away from the rest to go swimming alone.
"The teacher had finished his lesson and was on his way back to school with the pupils in tow. The boys may have broken away to swim and died in the process . It was unfortunate," he said.
The bodies were fished out of a creek by other pupils from the upper classes.
South Mugirango MP Sylivanus Osoro sent condolences but asked for investigations.
County Police chief Jebel Munene said," We are leaving nothing to chance."
Area Ward Rep Andrew Kimonge described the incident as 'perturbing'.
He asked security agencies to get all facts surrounding the happenings.
