RTE reported the development stating it is believed account holder is in the Republic
The PSNI probing online abuse mocking the late son of DUP MLA Diane Dodds have contacted gardai for assistance, it has been reported.
It is understood officers in Northern Ireland believe the person responsible is based in the Republic.
The Upper Bann representative's son, Andrew, was born with spina bifida and died in 1998, aged eight.
Mrs Dodds was targeted by an anonymous Twitter account, which is no longer active.
On Thursday social media giant Twitter performed a U-turn, stating the offensive tweet sent to Mrs Dodds broke the company’s rules. Previously it claimed the message did not break its safety policies.
Those who reported the tweet received a message from Twitter, stating: “Thanks again for letting us know. Our investigation found this account violated Twitter rules.”
RTE, which reported the the garda connection on Saturday, said the PSNI’s cyber crime unit had identified the account holder south of the border.
Mrs Dodds received messages of support from other politicians following the incident on New Year's Eve.
Mrs Dodds said she was “overwhelmed” with messages of support she received after the tweet was sent.
"I have been truly humbled and touched by the groundswell of support and encouragement from across Northern Ireland and I have no doubt that the universal revulsion at these disgraceful actions forced Twitter to act,” she added.
She described the online abuse as "callous and malicious".
PSNI officers interviewed Mrs Dodds about the tweet at her constituency office in Co Down on Tuesday, said the BBC.
The PSNI has been contacted for comment.