Can old write.lock files in index location be removed ?

Hi,
Sometimes we get issues raised about search (e.g. work item search) being faulty and our recourse has been to
run the associated repotools -reindex.  Today we got another issue on the same vein and I noticed numerous files in the index location named ...*.write.lock from various dates.   I'm thinking it's safe to remove them, but would like to be sure.  I could also guess that their presence might also preclude updating of the associated index data.

TIA

Kevin