sql server – Finding groups which have two values in another column

Given the following sample rows:

MTYPE RNO VAL
S     1   V1
S     1   V2
S     1   V3
R     1   V4
S     2   V5
S     2   V6
R     3   V7
R     3   V8

How can I list groups of RNO which has both ‘R’ and ‘S’ in any of its rows in MTYPE column. In the above sample data the result should be:

MTYPE RNO VAL
S     1   V1
S     1   V2
S     1   V3
R     1   V4

As RNO=1 group has both S and R rows in MTYPE column.