Fetch results using Collections in Search and Promote

Hi,

I am trying to fetch search results using Collections feature in Search and Promote.

I have two index files site1_index, site2_index where site1_index has two products which are also present in site2_index. I am able to fetch results for site2 collection but not for site1 collection. If I remove site2_index from URL entry point then able to see results for site1 collection.

URL Entrypoints

index:site1_index

index:site2_index

Collections

site1 regexp index:site1_index*

site2 regexp index:site2_index*

Any idea how we can show products for site1 and site2 in respective websites?