Mr McGarrigle was also a member of the Irish Republican Socialist Party.
The Police Service of Northern Ireland (PSNI) said that officers gathered evidence, and after the funeral seized clothing and other items.
Separately, police also made two arrests in Strabane on Tuesday as part of an investigation into suspected crimes linked to the INLA.
Two men, aged 59 and 64, were arrested under the Terrorism Act and are currently in custody.
A 40-year-old man was also arrested in Londonderry on Monday night on suspicion of terrorism offences.
He remains in custody.