Estoy tratando de hacer que las subredes anidadas funcionen utilizando jqGrid con datos locales. He buscado por todos lados pero no he podido encontrar una solución. Aquí hay una muestra simplificada de mi código:

var mainGridData =
    [
        // main grid data
        { id: "m1", col1: "11", col2: "12" },
        { id: "m2", col1: "21", col2: "22" },
        { id: "m3", col1: "31", col2: "32" }
    ];
var firstSubgrid =
    {
        m1: [
            // data for subgrid for the id=m1
            { id: "s1a", c1: "aa", c2: "ab", c3: "ac" },
            { id: "s1b", c1: "ba", c2: "bb", c3: "bc" },
            { id: "s1c", c1: "ca", c2: "cb", c3: "cc" }
        ],
        m2: [
            // data for subgrid for the id=m2
            { id: "s2a", c1: "xx", c2: "xy", c3: "xz" }
        ]
    };
var secondSubgrid =
    {
        s1a: [
            // data for subgrid for the id=m1
            { id: "2s1a", d1: "2aa", d2: "2ab", d3: "2ac" },
            { id: "2s1b", d1: "2ba", d2: "2bb", d3: "2bc" },
            { id: "2s1c", d1: "2ca", d2: "2cb", d3: "2cc" }
        ],
        s2a: [
            // data for subgrid for the id=m2
            { id: "2s2a", d1: "xx", d2: "xy", d3: "xz" }
        ]
    };


//------------
$("#grid").jqGrid({
    datatype: 'local',
    data: mainGridData,
    colNames: ['Column 1', 'Column 2'],
    colModel: [
        { name: 'col1', width: 200 },
        { name: 'col2', width: 200 }
    ],
//Subgrid1...
    subGrid: true,
    subGridRowExpanded: function (subgridDivId, rowId) {
        var subgridTableId = subgridDivId + "_t";
        $("#" + subgridDivId).html("<table id='" + subgridTableId + "'></table>");
        $("#" + subgridTableId).jqGrid({
            datatype: 'local',
            data: firstSubgrid[rowId],
            colNames: ['Col 1', 'Col 2', 'Col 3'],
            colModel: [
                { name: 'c1', width: 100 },
                { name: 'c2', width: 100 },
                { name: 'c3', width: 100 }
            ],
      //Subgrid2...    
            subGrid: true,
            subGridRowExpanded: function (subgrid2DivId, subRowId2) {
                var subgrid2TableId = subgrid2DivId + "_t";
                $("#" + subgrid2DivId).html("<table id='" + subgrid2DivId + "'></table>");
                $("#" + subgrid2TableId).jqGrid({
                    datatype: 'local',
                    data: secondSubgrid[subRowId2],
                    colNames: ['Col 1', 'Col 2', 'Col 3'],
                    colModel: [
                        { name: 'd1', width: 100 },
                        { name: 'd2', width: 100 },
                        { name: 'd3', width: 100 }
                    ],
                });

            }                
        });
    }
});

¿Alguna idea por ahí?