Help with SQL query (minutes to hh:mm)

I have a query like this:

select u.DEPARTMENT as DEPARTMENTUP, sum(w.SUMTIME) as TIMEUP from USERS u, WORKTIMES w
where u.CODE=w.CODE and w.INTIMETEXT='Business' and w.INTIME >'1.3.2012' and w.INTIME <'1.4.2012'
group by u.DEPARTMENT
order by u.DEPARTMENT asc

Field SUMTIME in WORKTIMES table is FLOAT data type and gives
time value in minutes.

How to format SQL Query so I can get TIMEUP(SUMTIME) column as
hh:mm format?