Searching on a field from multiple rows matching a groupId

[Jerry Malcolm]

I have a table where several rows have the same value in a 'groupId' col. I need to select the groupId if "abc" is found in colX in any row in a specific 'group' of rows AND "xyz" is also found in colX in any row in the same group rows (doesn't have to be the same row). In other words, both abc and xyz have to exist somewhere in colX in rows with the same groupId. I've been coding SQL for many years. But this one has me stumped. I think it may have something to do with grouping and concat. But I'm at a standstill.

Example:
NDX GROUPID COLX
1 1 aaa bbb abc ccc
2 1 ddd eee fff
3 1 ggg xyz
4 2 abc hhh iii
5 2 jjj kkk
6 2 lll mmm

The query should return groupid 1 since abc is found in ndx 1 and xyz is found in ndx 3, both a part of groupid 1. It should not return groupid 2 since even though abc is found in ndx 4, no record with groupid 2 contains xyz.

Can someone help me out with the magical MySQL incantation to query this?

Thanks in advance.

Jerry